Lung cancer is the leading cause of cancer death for both men and women. The p16 tumor suppressor gene is inactivated by aberrant promoter hypermethylation in a large percentage of non-small cell lung cancers (NSCLC). In order to identify effective therapies for lung cancer and further understand the mechanisms of de novo methylation, the following specific aims will be addressed. I. To determine the efficacy of liposome-mediated delivery of the p16 gene for treatment of NSCLC. II. To characterize the transcriptional regulation of the rat p16 promoter. III. To determine if O6MG adducts initiate methylation of the rat p16 promoter which leads to transcriptional repression. These studies will provide justification for the development of Phase I clinical trials, may identify one of the initiating factors for aberrant methylation of the rat p16 promoter, and will provide the foundation for understanding transcriptional repression by methylation.